Endstone cap assembly



July 24, 1951 E. w. DREscHER 2,561,690-

ENDSTONE CAP ASSEMBLY Filed Feb. 23, 1949 Patented July 24, 1951 i UNITED STATES PATENT OFFICE ENDSTONE CAP ASSElVLBLY` l Ernest W. Drescher, Manheim,;"l1ownship, Lancaster County, Pa., assignor to Hamilton Watch Company, Lancaster, Pa.

Application reb'rafy 23, 1949, serial No. 77,769

This invention relates to a balance endstone cap assembly and the method of making the same.

The endstone cap assembly serves as a means for supporting the balance staff and as acenter about which the regulator pins are turned. The entire assembly is supported in the balance cock and is disassembled for even the smallest of repair jobs on the watch. To prevent reshaping of the overcoil of the hairspring to conform to the path of the regulator pins, it is necessary that when the endstone cap assembly is replaced in the balance cock that the same concentricity be maintained as was formerly present before the parts were disassembled. With the present day construction, it is impossible to return the parts to the exact same relative position because the tolerance is greater in the setting of the endstone cap assembly than the distance between the regulator pins and the hairspring overcoil. This necessitates reshaping of the overcoil and a possible throwing of the watch out of time necessitating a retiming of the watch, which requires along period of time.

The object of the present invention is to provide a method of making and assembling an endstone cap assembly with the balance cock so that after the overcoil of the hairspring has once been shaped to conform to the path of the regulator pins and after a subsequent disassembling of the parts, the reassembling operation will return the parts to the same relative positions which they occupied before being taken down. This relieves the necessity of reshaping the overcoil of the hairspring.

A further object of the present invention is to provide an endstone cap assembly in which a relative concentricity of all its parts with the balance cock is maintained through repeated assembling and disassembling operations.

A still further object of the present invention is to provide a cam locking means for holding the parts in tight relationship.

A still further object of the present invention is the method of making the endstone cap so that the tolerance in fitting the endstone cap to the balance cock may be maintained at a minimum.

A further object of the present invention is to provide a circular contact in the balance cock into which the endstone cap assembly is tted so that the assembling and disassembling of the endstone cap and balance cock will make no change in the concentric relation one with the other.

A still further object of the present invention 2 is toprovide three points of contact by means of which the endstone cap may be assembled'with the balance cock repeatedly without disturbing the concentricrelation of the two.

vIt is a further object of the present invention to provide an endstone cap formed with swedged feet and having an interrupted circumference to serve as a bearing for the regulator.

The invention is shown in the accompanying drawing in which:

Figure 1 is a top plan view of the assembled invention.

Figure 2 is a, section on line 2-2 of Figure 1.

Figure 3 is a bottom view of the endstone cap, showing the original endstone cap in dotted lines and the iinished turn cap in solid lines.

Figure 4 is a bottom view of the endstone cap and balance cock, particularly showing the cam used to wedge the two together.

Figure 5 is a cross sectional view of the endstone cap showing the original extent of one of the pins on the dotted lines.

Referring more particularly to the drawing, the balance cock 1 is shown supporting the endstone cap 8 which is tted with the endstone jewel 9 and carries the regulating arm l0.

This endstone cap 8 serves as a center pin for the regulating arm lll and as the endstone cap is mounted in the balance cock 1, the closeness of t between the endstone cap and the balance cock is extremely important as regards the movement of the regulator arm with relation to the balance cock.

Mounted in the balance cock l is the olived hole jewel Il which serves as a pivot for the balance staff I2 on which is mounted the collet I3. A hairspring I4 is secured to the collet I3. The outermost coil l5 of the hairspring is overcoiled and formed, for a small section, in a true circular curve which conforms to the path of the regulator pins.

When the watch is taken apart for cleaning, the reassembling of the endstone cap and balance rcock is extremely important to the timekeeping of the watch as the outermost coil of the hairspring must resume its exact position in order for the regulator pins to function. It is, therefore, necessary that the endstone cap and balance cock be reassembled in exactly the same relationship as they were before.

As is Well known, the regulator pins change the eilective length of the hairspring by the pivoting of the regulator arm about the endstone cap, moving the pins on that section of the hairspring which conforms to the path of the regulator pins.

It is, therefore, seen how necessary it is that the regulator pins move in a curve which has as its center the endstone cap.

In the formation of an endstone cap which can be effectively removed and replaced on a balance cock and maintained in original position, a blank cap is formed as shown in dotted lines in Figure 3 at l1 and feet I8 are swedged on the cap. A turning operation produces a conguration shown in solid lines in Figure 3 at I9 having three lips 20 of slightly larger diameter than the main body 2| of the cap. In the turning operation the outside edges of the pin 22 are turned to the same diameter as the body of the cap producing in effect a cylinder which is fitted into the holes 2l of the balance cock.

The pins I8 are undercut as at 24 on their inward surfaces and a cam 25 having pin engaging carn surfaces 26 is turned by means of a screw slot 21 into engagement with the undercut portions of the pins to draw the endstone cap downward against the balance cock, the cam bearing against the blance cock at 21 (Figure 2).

What is claimed is:

An endstone cap and balance cock assembly, 25

comprising a balance cock formed with three openings, the centers of which are concentric with ERNEST W. DRESCHER.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,015,905 Marti Oct. l, 1935 2,306,233 Smith l- Dec. 22, 1942 FOREIGN PATENTS Number Country Date Y 13,902 France Mar. 11, 1897 132,962 Switzerland July 16, 1929 

